Why do we dream? What scientists think and where they disagree

Scientists do not agree on why people dream. Several theories exist, and the leading one holds that dreaming is tied to the consolidation of memories during sleep. Sleep experts continue to debate the question, and one source notes it may be impossible to conclusively prove any single theory. [1] [2]

The Cleveland Clinic describes the prevailing theory as one in which dreaming helps consolidate and analyze memories, such as skills and habits, and may act as a rehearsal for situations faced in the daytime. At MIT's McGovern Institute, researcher Dheeraj Roy says newly formed memories are gradually stabilized into longer-term storage during sleep, and that dreaming is influenced by this process. Most dreams are built from people, places, emotions and experiences we have already encountered, though the pieces are recombined into odd scenarios. [2] [3]

A Cambridge Core review adds detail. Dreams in REM sleep tend to be more vivid, emotional and bizarre, while NREM dreams more often reflect recent episodic memories. In one study, people who watched a film in a lab were more likely to dream about the lab setting, such as wearing electrodes, than about the film itself. Memories in dreams are usually not exact replays. The review also says it remains unclear whether dreaming uses the same brain pathways as waking learning and memory. [4]

Psychologist Mark Blagrove, speaking on an American Psychological Association podcast, lists several other proposals. Threat simulation theory says dreams let us practice overcoming dangers in a safe setting, such as being unprepared for an exam. Emotion-processing theories include a fear-reduction idea, in which we dream of our fears in a way that diminishes them. [5]

The Sleep Foundation lists further ideas: dreaming as mental housekeeping that clears partial or unnecessary information, and as a distorted instant replay of recent events. J. Allan Hobson, as summarized by sleepeducation.org, argues that REM sleep provides a virtual reality model of the world and that dreams help tune the brain for wakefulness. The Cambridge review also mentions older proposals that dreams express unconscious desires or arise from random neural activity. [1] [6] [4]

Blagrove notes an epiphenomenal view, held by many scientists and members of the public, that dreams serve no purpose. On this account dreaming is a spillover of daydreaming into sleep, which evolution has not removed because it does little harm. The Sleep Foundation describes the same view as dreaming being a by-product of sleep without essential purpose or meaning. [5] [1]

Even the definition of dreaming is not unanimous. Some researchers define it as thoughts and feelings experienced during sleep, others as a mix of visual, motor, verbal, emotional and cognitive processes. The sources call memory consolidation the prevailing or very current theory, but they do not present it as proven, and the other theories are not ruled out. [4] [5]